This is an Investigator-Initiated Resource-Related Research Project Application (R24) to create a biorepository of both biological samples and genetic data for patients with World Health Organization (WHO) Group 1 pulmonary arterial hypertension (PAH). Once established, this national resource will significantly enhance the conduct of basic, translational, and clinical research for this devastating and lethal disorder. The biological samples collected and genetic data generated from these samples will enable unprecedented hypothesis-driven science which to date has not been possible for PAH or other forms of pulmonary hypertension. The National Biological Sample and Data Repository for PAH will represent an unprecedented collaboration between academic PH centers across the United States whose efforts will lead to the collection of the largest cohort of PAH patients either nationally or internationally. The resulting cohort of patients and data can provide the much needed catalyst for tour de force research efforts aimed at accelerating the development of novel therapies through the identification of novel pathways or genetic factors contributing to the disorder. This repository undeniably addresses a national need that fulfills the strategic vision of NHLBI and provides truly unique resources to the broader scientific community. To establish this national resource, we propose to: 1) Work with PAH academic centers in the United States to collect and maintain biological material from no less than 2500 WHO Group 1 PAH patients. Samples to be banked on each patient include total genomic lymphocyte DNA, EBV transformed peripheral blood lymphocytes, and plasma; 2) Generate both genome wide SNP genotype data and BMPR2/ALK1 sequence/MLPA data on 2500 patients enrolled in the bank. The SNP data will be cleaned prior to its deposition in the database of Genotypes and Phenotypes (dbGaP); 3) Widely promote and distribute samples and genotype/sequence data maintained at the National Biological Sample and Data Repository for PAH. All biological samples, clinical data, as well as the SNP genotype and sequencing data for the patients will be made available to the scientific community.